1. Field of the Invention
This invention is in the area of biosensors, and encompasses nanoparticles whose presence is detectable by two means, magnetic and visual. The nanoparticles have a core/shell structure with a magnetic core and a fluorescent semiconductor shell.
2. Description of Background Art
Passivated magnetic nanoparticles with core shell structure have recently been described in U.S. patent application Ser. No. 10/355,162 filed on Jan. 31, 2003 and based on provisional U.S. patent application 60/307,693 filed Apr. 4, 2002 by the inventors of this patent application, both applications are incorporated herein by reference in their entirety. In the invention described in the incorporated patent applications, nanoparticles having a core/shell structure with a magnetic core and a metal oxide shell are described and claimed. The shell passivates the core to protect against further oxidation.
U.S. Pat. No. 6,048,515 describes multilayered nanoparticles having a magnetic core and at least two layers of coatings thereon. The particles of this invention may be detected magnetically or visually because of the reddish brown color of the core. The nanoparticles of this invention are said to be useful for diagnostic and therapeutic purposes.